Home › Forums › Help/Technical Questions › big muff american reissue very low output
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March 8, 2011 at 11:22 pm #81440khandleyMember
i’ve been wrestling with my big muff for a while to bring it back to life
i’ve seen a lot of posts of things like this or similar but they seem to get abandoned
when the pedal is off, it bypasses perfectly but when engaged the volume pot has to be up all the way to hear something.
you can hardly call it output.
i’ve replaced the vol pot and checked all wiring and everything seems fine
don’t really have any money to get it fixed at the guitar shop
any diy help would be appreciated
March 9, 2011 at 12:55 am #114581The EH ManModeratorHave you tried audio tracing?
May 24, 2011 at 5:49 am #115287Frobro808MemberHey guys im new here and this is my first post! Im sorry to have zombied this thread…
I have the same problem and bynthe time I have enough signal, the noise and the actual effect are the same level. And what exactly is audio tracing.December 23, 2011 at 7:15 am #116578derekbMemberactually having the same issue on a spare big muff pi I have lying around, has anyone ever figured out the likely culprit for this? effects appear to work but unless you crank volume to max on the pedal, you cant even hear anything, and even then what you can hear is muffled by pedal hum. Any solutions?
December 23, 2011 at 8:22 pm #116584scottvMemberIt could be a number of issues, an audio trace is I believe like an “audio probe” there is a step by step guide on DIY stompboxes dot com on how to do this, basically its using a cable with a signal source plugged into it on one end (something that gives a constant sound, plucking a guitar is too cumbersome, so maybe a portable cd player or ipod) and capacitor on one lead of the opposite end and the other lead grounded. use the open lead of the capacitor as “the probe” contacting various places on the circuit board, not randomly as you should “trace” through the circuit from start to end, the output of the circuit is plugged into an amp to listen for the input signal, what this will find is if there is:
bad solder point or trace on the circuit bad
or
bad component (capacitor, transistor, diode… resistors are tougher to destroy but…)
December 23, 2011 at 8:33 pm #116585The EH ManModeratorCheck at the center lug of the Volume control. If it’s loud there it’s probably a footswitch issue.
Check the center pin of each transistor for signal. If it’s there then it’s got through the previous stage OK.December 24, 2011 at 2:10 am #116590derekbMemberQuote:It could be a number of issues, an audio trace is I believe like an “audio probe” there is a step by step guide on DIY stompboxes dot com on how to do this, basically its using a cable with a signal source plugged into it on one end (something that gives a constant sound, plucking a guitar is too cumbersome, so maybe a portable cd player or ipod) and capacitor on one lead of the opposite end and the other lead grounded. use the open lead of the capacitor as “the probe” contacting various places on the circuit board, not randomly as you should “trace” through the circuit from start to end, the output of the circuit is plugged into an amp to listen for the input signal, what this will find is if there is:bad solder point or trace on the circuit bad
or
bad component (capacitor, transistor, diode… resistors are tougher to destroy but…)
sounds interesting, any chance you ahve a link to the guide?
December 24, 2011 at 3:42 pm #116595scottvMemberhttp://www.diystompboxes.com/wiki/index.php?title=Debugging
2nd section from the top is on using an audio probe.
December 24, 2011 at 7:50 pm #116596derekbMemberthanks for the link
On some additional fiddling I found what seems to be the problem, the tone knob is cutting out completely once turned past 12 o clock.
On further inspection, it seems the Tone knob cuts out the output unless I pull the knob physically upwards away from the unit. Should I just replace the potentiometer?
December 25, 2011 at 5:27 am #116600scottvMemberit might be the pot, i would use a multimeter on it and check the resistance at various points in its rotation. that may give you a clue if its bad.
December 25, 2011 at 5:32 am #116601derekbMemberQuote:it might be the pot, i would use a multimeter on it and check the resistance at various points in its rotation. that may give you a clue if its bad.it certainly seems to just be the pot, once the knob is lifted about a millimeter out of the socket it rests in it clicks back in, and theres no physical movement on any other component since its secured in place. will replace and see what happens
January 14, 2012 at 7:44 pm #116757warthogMemberThis is exactly what is happening with my muff and the tone knob! any updates on your fix?????
a
January 14, 2012 at 8:20 pm #116758derekbMemberQuote:This is exactly what is happening with my muff and the tone knob! any updates on your fix?????a
actually yes, the pot would lose contact if not holding the knob slightly vertically up, so as a ghetto solution I inserted a small rubber o-ring into the gap created when pulling the pot stem. This keeps the knob held up and in contact, it adds some resistance to turning, but hey, it works!
January 14, 2012 at 9:30 pm #116759warthogMemberQuote:Quote:This is exactly what is happening with my muff and the tone knob! any updates on your fix?????a
actually yes, the pot would lose contact if not holding the knob slightly vertically up, so as a ghetto solution I inserted a small rubber o-ring into the gap created when pulling the pot stem. This keeps the knob held up and in contact, it adds some resistance to turning, but hey, it works!
THanks! I’ll give it a try.
A
January 14, 2012 at 10:39 pm #116760The EH ManModeratorI have seen this on some other EH pedals but not on Big Muffs. What you can do is open the pot up and bend the wiper contacts out a bit then reassemble the pot.
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